Stabilization of chlorinated hydrocarbons



United States Patent 3,02,297 STABILIZATION 0F CHLORINATED HYDROCARBONS Fred S. Hirsekorn and John H. Rains, Wichita, Kane, as-

signors to Frontier Chemical Company, Division of Vulcan Materials Company, Wichita, Kane, a corporation of New Jersey No Drawing. Filed Apr. 7, 1960, Ser. No. 20,541 Claims. ((31. 260-6525) This invention relates to the stabilization of halogenated aliphatic hydrocarbons and to the stabilized composition, the stabilizer being diallylamine, tripropylene (or other unsaturated aliphatic hydrocarbons having an average number of carbon atoms of about nine per molecule) and mixtures thereof.

It is known that chlorinated hydrocarbons such as perchlorethylene have a tendency to decompose during storage, shipment and sometimes use. This tendency becomes more pronounced when the chlorinated hydrocarbon is in contact with metals such as copper, steel, aluminum, etc. and/or is exposed to heat, moisture and light. Such decomposition results in the formation of hydrogen chloride and phosgene, among other objectionable decomposition products. These may cause serious corrosion of metal in dry cleaning machines and metal degreasing units. The acidic products of decomposition may be detrimental to fabrics and to many dyes. Cousequently, materials which will inhibit or prevent the decomposition of these chlorinated hydrocarbons are usually added. 7

In a broad embodiment the present invention comprises adding to a chlorinated hydrocarbon a small but effective amount of a stabilizer composed of diallylamine, an unsaturated branched chain hydrocarbon such as tripropylene, nonene and the like and particularly of mixtures of the amine and the hydrocarbon. Each of these stabilizers may be added in an amount from about 0.005 to about 1.0% by weight of the composition, although as a rule the stabilizers are not required in amounts exceeding about 0.2%of each. Usually the amount of diallylamine is less than that of the tripropylene or similar branch chain hydrocarbons. Satisfactory proportions are shown in the accompanying Table I.

The chlorinated hydrocarbon with which the invention is particularly concerned is perchlorethylene, although it is also applicable to other low boiling chlorinated hydrocarbons such as chloroform, methylene chloride, dichloroethylene, trichlorethylene and the like.

The low boiling chlorinated hydrocarbons are widely used in the dry cleaning industry where the problem of decomposition of the solvent may become acute due to corrosion of equipment and adverse eflect upon the garments cleaned. In the experiments which are set forth hereinafter, the effectiveness of the stabilizer was determined following the method of the National Institute of Dry Cleaners, Method N.I.D. Specification 3-55.

Briefly, this method consists of refluxing perchlorethyl ene or other halogenated hydrocarbon under test, in a flask in the presence of water and strips of copper. One

ice

hundred ml. of the stabilized perchlorethylene ismeasured into a 300 ml. round bottom flask and 0.2 ml. of distilled water is added. Strips of electrolytic copper 2.0 x 7.5 x 0.005 cm. are thoroughly cleaned and weighed. One strip is inserted in the flask so asto be substantially completely immersed in the liquid. A Soxhlet extractor having a volume of approximately ml. is attached to the flask and a second copper strip is inserted into the extractor. A small Allihn condenser is mounted on top of the Soxhlet extractor and a third copper strip is placed in the condenser so that the perchlorethylene condenses on the strip. A 100 watt frosted Mazda incandescent light bulb is placed one inch from the extractor vapor tube to supply energy for photochemical oxidation. The flask is heated by suitable means so as to reflux the composition at a rate which causes the extractor to empty about once every eight to ten minutes. These conditions are maintained for the duration of the test which is usually '24 hours but may be longer. The condenser is attached to a water scrubber to absorb any hydrogen chloride which may be evolved during the test.

After this portion of the-test is completed, the flask is cooled and a quantity of water equal to the perchlorethylene sample is poured through the condenser and extractor into the flask to absorb any acid. The contents of the flask are shaken and the acidity developed during the test is determined by sodium hydroxide titration using bromothymol blue as the indicator.

The loss in weight in milligrams of the copper strips suspended in the flask, extractor and condenser are determined and totaled. According to paragraph 14 of the N.I.D. Specification 355 a maximum .loss of mg. (0.001 gram per square centimeter exposed) is permissible. As a practical matter for satisfactory commercial stabilization of the dry cleaning solvents such as perchlorethylene, the loss should be less than about 10 mg.

over a 24 hour exposure period for satisfactory stabilizer performance.

In view of the fact that the perchlorethylene or other solvent is recovered by distilling'it so as to separate the materials extracted during the dry cleaning operation, the stabilizer should boil in a range such that it will pass overhead with ,the solvent during the distillation. It should leave no spots or stains on fabrics after the solvent has been completely evaporated following completion of the dry cleaning cycle. The color of the stabilized solvent must remain water white after stabilization. The residue after solvent evaporation must be below about 0.016 gram per m1. of solvent. Preferably the stabilizer should itself be stable and should stabilize the chlorinated hydrocarbons against decomposition both in dark storage and when exposed to light.

In Table I are shown the results of a series of tests performed in accordance with the above described method in which perchlorethylene with and without stabilizer was examined for acidity and for loss of weight of the copper strip during the test. Tests with each of the stabilizers alone and of the stabilizers in combination are given for 24 hour duration. One test at 72 hours exposure with the combined stabilizer is included.

TABLE I Stabilization of Perchlorethylene with Diallylamine-Tripropylene Weight Percent DurapH Weight Loss Men of Acidity, Test, p.p.m.

Diallylamine Trlpropylene hrs. Before After Flask Extractor Condenser Total 24 7. 6 2.1 382 5.9 6. 1 1 207. 3 219. 3 0. 0087 24 0 0. 9 l. 0 0. 9 2. 8 0. 0204 24 0 1. 1 l. 0 0. 6 2. 7 0. 0472 24 0 1. 2 0. 7 0. 8 2. 7 0. 0496 24 9. 2 8.5 0 0.4 0. 4 0.2 1. 0 0. 0986 24 9. 1 8. 6 0 0. 2 0. 6 0. 2 1. 0 0. 0193 72 0 1. 2. 2 1. 2 4. 9 0. 0708 24 0 6. 2 0.0700 24 0 3. 3 0 24 0 1. 5 1. 4 1. 0 3. 9 0 24 0 5. 0 0 24 0 1. 2 1. 3 0. 9 3. 4 0 24 0 1. 4 1. 4 0. 4 3. 2 0 24 0 3. 6 1. 6 2. 4 7. 6 0 24 0 0 9 5 0 3. 0 1. 6 1. 8 7. 3 0. 0099 24 0 1. 2 4. 3 18. 9 24. 4 0. 0198 24 ll 1. 2 l. 5 5. 3 8. 0 0. 0486 24 0 0. 5 3. 7 4.0 8. 2 0.1000 24 7 5 7. 7 0 1. 6 3. 6 11.4 16.6

1 Copper strip badly corroded.

The data show that the development of acid during the test is reduced by either stabilizer alone but that the combined stabilizer is more efliective than either component. The combined stabilizer has an additional advantage which does not appear from the results shown in the table, namely, that upon prolonged storage the dual stabilizer reduces or completely-prevents the deposition of amine salts from the perchlorethylene which sometimes may occur when the amine is used by itself.

The dual stabilizer has been employed in commercial dry cleaning establishments wherein the solvent is reclaimed by distillation up to 11 times without addition of fresh solvent except to replace processing losses and the recovered solvent has been found to be stable according to the N.I.D. test. The results of the field tests using the dual stabilizers in amounts of 0.0050% diallylamine and 0.0700% tripropylene establish that the stabilwith other halogenated hydrocarbons, the test was carried out using chloroform as the halogenated hydrocarbon. The chloroform was freshly prepared and was placed in clear glass bottles with and without a steel strip or coupon in comparable bottles. In one set, amylene which is a stibilizer commonly used in chlorofrom was included and in another the dual tripropylene-diallylamine stabilizer was used. The samples were analyzed for acidity after two weeks exposure by washing each sample with neutral distilled water and then titrating with standard sodium hydroxide using bromothymol blue "as the indicator. The acid is reported in terms of hydrogen chloride. The results (Table II) show that the dual stabilizer is cfiective in preventing the decomposition of chloroform during storage and exposure to incident light.

TABLE H chloroform Stability With Various Stabilizers The dual stabilizer is less expensive than many stabilizers now employed. The tripropylene may be a byproduct of the polymerization of propylene or may be a by-product resulting from the alklation of isobutane and the like, with propylene. It may boil over a range which means that it may contain C to C unsaturated branched chain hydrocarbons. Ordinarily it is used in an amount of two to three times that of the diallylamine.

The sample employed in the herein reported experiments was a mixture of branch chain olefins having an average of 9 carbon atoms per molecule. The 5% distillation point was about 250 F. and the point was about 305 F. The unsaturation was 97% by volume and molecular weight about 127.

Similar effects were obtainable with nonene, a branch chain olefin comprising a mixture of olefins about 99% of which are unsaturated and have a boiling range from about 260 to about 290 F.

Ordinarily the stabilizer is added at the point of manufacture and packaging of the perchlorethylene. It is added before any substantial decomposition can occur; The finished composition is usually shipped in bulk in tank cars or trucks although quite frequently it is shipped in fifty gallon drums or smaller containers. The dual stabilizer of this invention does not impart objectionable odor or color to the stabilized composition.

We claim as our invention:

1. A stabilized halogenated hydrocarbon containing a small but effective proportion of a stabilizer selected from the group consisting of diallylamine and tripropylone, and mixtures thereof, the proportion of diallylamine being from about 0.0016% to about 0.2% by weight, and the tripropylene being about 0.005% to about 1% by weight of the halogenated hydrocarbon.

2. A stabilized low boiling chlorinated hydrocarbon composition containing a small but effective'amount of a stabilizer selected from the group consisting of diallylamine and tripropylene, and mixtures thereof, in a proportion of about 0.005 to about 1% by weight of the composition.

3. Stabilized perchloroethylene composition containing tripropylene and diallylamine each in proportions within the range of from about 0.005 toabout 1.0%.

4. The composition of claim 2 wherein the stabilizer is diallylamine.

5. The composition of claim 2 wherein the stabilizer is tripropylene.

6. The composition of claim 2 wherein the stabilizer is a mixture of diallylamine and tripropylene.

7. A method for stabilizing a halogenated hydrocarbon from decomposition under conditions of storage and use which comprises adding thereto a small but etfective amount of a stabilizer selected from the group consisting of diallylamine and tripropylene and mixtures thereof, the proportion of diallylarnine being from about 0.0016% to about 0.2% by weight, and the tripropylene being about 0.005% to about 1% by Weight of the halogenated hydrocarbon.

8. A process for stabilizing a low boiling chlorinated hydrocarbon against oxidative decomposition which comprises adding thereto a small but elfective amount of a stabilizer selected from the group consisting of tripropylone and diallylamine and mixtures thereof, the proportion of stabilizer being about 0.005% to about 1.0% by weight of the composition.

9. A process for stabilizing perchlorethylene against 1 oxidative decomposition which comprises adding thereto a small but efiective amount of a stabilizer selected from the group consisting of tripropylene and diallylamine and mixtures thereof, the proportion of stabilizer being about 0.005% to about 1.0% by weight of the composition.

10. A process for preventing the oxidative decomposition of perchlorethylene which comprises adding thereto tripropylene and diallylamine each in proportions within the range of about 0.005 to about 1.0%.

References Cited in the file of this patent UNITED STATES PATENTS 1,904,450 Harris Apr. 18, 1933 2,043,257 Missbach June 9, 1936 2,068,607 Olin Jan. 19, 1937 

1. A STABILIZED HALOGENATED HYDROCARBON CONTAINING A SMALL BUT EFFECTIVE PROPORTION OF A STABILIZER SELECTED FROM THE GROUP CONSISTING OF DIALLYLAMINE AND TRIPROPYLENE, AND MIXTURES THEREOF, THE PROPORTION OF DIALLYLAMINE BEING FROM ABOUT 0.0016% TO ABOUT 0.2% BY WEIGHT, AND THE TRIPROPYLENE BEING ABOUT 0.005% TO ABOUT 1% BY WEIGHT OF THE HALOGENATED HYDROCARBON. 